An electrical load may be controlled by supplying control signals to a current-control device. The control signals may originate as digital signals and be converted to analog control signals by a digital-to-analog converter (DAC).
Offsets can interfere with the ideal operation of such drive circuits. For example, some DACs may provide a non-zero analog output signal even when the digital signal being converted specifies a zero output (positive offset). Some DACs may provide a zero output even when the digital signal being converted specifies a non-zero output (negative offset).
Such offsets can arise as a result of process variations in the manufacture of DACs. Consequently, two DACs of the identical type may exhibit different offsets. Other components in the signal path to the current-control device may also introduce offsets.
Even offsets that are small relative to the full range of the analog control signal can be problematic where fine control is required. For example, such offsets can make it impossible to determine the digital control signal necessary to effect the lowest possible non-zero current through an electrical load.
Offsets can be addressed by making circuits with high quality DACs and other components that have been selected to have very low or at least known offsets. However, high quality components are often much more expensive than standard components.
Another approach is to individually adjust circuits to compensate for offset in circuit components. Individual tuning of circuits significantly increases manufacturing cost and complicates manufacturing.
There is a need for cost-effective ways to compensate for offsets in DACs and other components of circuits used to drive electrical loads.